I still cannot accept the premise that D&D shapes culture when the opposite is so clearly obvious.
But without that premise, wherein lies the problem with sexism or the lack of sexism? Could one not just settle for the fact that dragonkin breasts are no more or less sexist than their target audience?
This goes to the good faith argument. To state 'dragonboobs are sexist and therefore wrong' you have to assert that they influence culture more than they are influenced by it.
Same with boobmail.
I wanted to call attention to your post, since I think that the point you raise goes straight to the heart of the matter. Simply put, there is a very large debate going on across (virtually all of) fandom about whether art imitates life, or life imitates art.
For those who believe that life imitates art, the idea that art, fiction, and media have the power to normalize and reinforce attitudes is assumed, and it thus follows that the media must therefore be made to stop depicting immoral values in a positive way (if not stop depicting them altogether), replacing these with positive values, since these will in turn promulgate and normalize social justice within society at large. Fixing what the media displays is, in this line of thought, a big step forward in fixing what's wrong with our culture. Those who disagree with that are, at best, complicit in maintaining an unequal status quo that continues to oppress those that aren't privileged in society (at worst, those who disagree are actively fighting the empowerment of people that have already been disenfranchised for a very long time).
On the other side of the debate are those who believe that art imitates life. To these people, media and fiction have very little power (if any) to influence or normalize attitudes among mature, mentally competent people. As such, this camp sees no real moral issues to be found in the mass media, since the mass media is largely a reflection of our cultural identity, rather than a creator of it. Ergo, the idea of needing to change the media to de-emphasize perceived immorality and promote morality is a waste of time at best (and an attack - rather than a debate - against those with different ideals, at worst), since the only real way to "fix" the media is to correct the underlying problems with society at large.
Simply put, this is another iteration of a very old, very large debate; only the context in which it's taking place has changed.